1. Field of the Invention
This invention relates to an improvement of a medical image processor used for analyzing at least two comparison images which are obtained by simultaneously photographing an object such a fundus of an eye to be tested as a stereoscopic image or obtained by photographing the object at a different time as a time-lapsed image.
2. Prior Art
Heretofore, there is known a medical image processor used for analyzing at least two comparison images which are obtained by simultaneously photographing an object such a fundus of an eye to be tested as a stereoscopic image or obtained by photographing the object at a different time as a time-lapsed image.
A medical image processor of this type is used for analyzing a three-dimensional configuration of the eye fundus or changes of the eye fundus due to eye disease or the like.
In order to analyze a three-dimensional configuration of the eye fundus or changes of the eye fundus due to eye disease or the like, it is necessary to obtain a corresponding relation between a pair of comparison images. Heretofore, there is employed a method which will be described hereinafter, in order to obtain a corresponding relation between such pair of comparison images.
First, as shown in FIG. 1, a left image 1 and a right image 2 are simultaneously displayed, side by side, in a CRT monitor 3 as a pair of comparison images. Selected one of the images 1 and 2 is served as a reference image. Let us presume that the left image 1 has been selected as the reference image. Then, the operator sets a reference point K (positional ordinates X and Y) through a mouse or a keyboard. An easy spot for discrimination in the image is selected as this reference point K. Let us presume here that a branch spot between a blood vessel 4 and another blood vessel 5 in the left image 1 has been set as the reference point K. Thereafter, the operator sets a branch spot between a blood vessel 4' and another blood vessel 5' in the right image 2 as a corresponding point K' of the right image 2 corresponding to the reference point K by a mouse or a keyboard, while comparing the left image 1 with the right image 2.
Thus, there can be obtained a corresponding relation between the left image 1 and a right image 2. Three or more of such reference points K are usually set.
However, this conventional method has the problem in that it takes too long time to obtain a corresponding relation between the left image 1 and the right image 2. Since the left image 1 is compared with the right image 2 with naked eyes, a reproducible result is difficult to obtain and errors are substantially large. Moreover, since one of the images is sometimes seen in a somewhat distorted shape due to linearity characteristic of the CRT monitor 3, there exists errors originally in this method in which the left image 1 is compared with the right image 2 with naked eyes.
In the case of a three-dimensional measurement, this error is quite undesirable.
The reason is that in the case of a three-dimensional measurement, it is necessary to obtain an amount of displacement (disparity) of a picture element from the reference point. Height information (or depth information) is obtained with reference to the amount of displacement of the picture element from the reference point. Accordingly, if there exists an error at the time a corresponding relation is obtained between the left image 1 and the right image 2, this error results directly in error of the height information, thus making it difficult to perform a correct three-dimensional measurement. Moreover, in a stereoscopic photography, there is a fundamental difference in construction of an image between the left image 1 and the right image 2.
In addition, there is another problem in that the operator is required to pay too much attention (too much concentration).
In case of an analysis of the changes of the eye fundus due to eye disease or the like, the following procedure is taken.
As shown in FIGS. 2(A) and 2(B), an eye fundus image 7 as one of the comparison images is outputted as a hard copy 6 of a photograph or the like through a video printer. Then, a mark M serving as the reference point K is attached to the hard copy 6. Thereafter, only one or both of the comparison images are displayed in the CRT monitor 3. Then, while seeing the hard copy 6, the operator sets a corresponding point K' corresponding to the reference point K to the other eye fundus image 8 which is displayed in the CRT monitor 3 together with the eye fundus image 7. This method also involves the same problems as mentioned above. In FIG. 2(A), reference numeral 9 denotes a diseased spot.